| Susceptibility of nullisomic wheat dwarfs and their
respective gigas-plants to leaf-rust, Puccinia triticina
S. MATSUMURA and K. KATSUYA National Institute of Genetics, Misima, Japan Dwarf plants possessing 40 chromosomes (20II) , found among the offspring of the pentaploid hybrid, Triticum polonicum x T. Spelta, are nullisomics, deficient in a chromosome pair of the D-genome. Depending on which of the a-g D-chromosomes is missing, they are called a-g-dwarfs. The respective gigas-plants with 42 chromosomes found among the offspring of nullisomics are called a-g-gigas. They also may be termed D-nulli- and AB-tetrasomics. In order to examine the susceptibility of nullisomics and their gigas-plants to leaf rust, a-g-dwarfs and a-g-gigas were tested at the first leaf stage with Puccinia triticina 21B. One parent, T. polonicum, was susceptible, while the other, T. Spelta, showed resistance to rust. Because all e-dwarfs and their gigas-strains were susceptible, it has been concluded that the gene for resistance is located on the e-chromosome of the D-genome. A strain of g-dwarfs was susceptible, but a gigas-strain originating from another g-dwarf was resistant. The c-dwarfs and their gigas-plants exhibited resistance or moderate resistance and b-dwarf and its gigas-plants were resistant. Though a-dwarf was resistant, among a-gigas plants resistant and susceptible strains were observed. It has been assumed that the supernumerary chromosomes of resistant and susceptible a-gigas-strains were different. Among d- and f-dwarfs resistant and susceptible strains were found, and also the correspondent gigas-strains showed resistance and susceptibility, respectively. We supposed that more genes for susceptibility are located on the chromosomes of the A- and B-genomes, in addition to the epistatic genes of the D-genome. |